The present invention is directed to an in-line, inclined self-cleaning strainer for piping systems by which particulates are removed from the flowing medium in the piping system. There are a great variety of structures for strainers in piping systems which remove solids and particulates from the flowing medium. Examples of such strainers are basket-type strainers in which the flowing medium passes through a basket-like wire mesh, thereby trapping the sediment in the basket, and a Y-type strainer, with the flowing medium flowing through one branch of the "Y" into the other branch, in which the entrapped sediments may be released via a check valve or the like. The basket-type strainer is typically used in horizontal disposition, while the Y-type is generally used in vertical orientation, although it may also be used in horizontal orientation. However, what is important is that elements within the piping system be protected from invasion by solid particulates, and the like, so as not to impair and/or cause breakdown of the parts. For example, it is imperative that strainers be placed in close proximity to inlet of pumps. Strainers are also used for protecting condensers, heat exchangers, meters, spray nozzles, turbines, traps, and the like. Without strainers, piping systems would have considerably shorter life span than at present.
The same recurring problem with all strainers is that, at some juncture, they must be cleaned from the debris imbedded in the screen mesh and the accumulated particulates in the drain. The simplest way of doing this is by manual operation in which an operator will remove the strainer from its connection to the piping system, and clean or replace it with a new mesh material. The strainer may also be cleaned by providing a spray nozzle that injects a spray against the screen for "back-flushing." During the flushing operation, a drain valve is opened which removes the evacuated debris from the piping system. Another type is an automatic self-cleaning strainer by which the flowing medium is never shut off, but is actually used to provide cleaning to the strainer, in contradistinction to the back-flushing technique where the system must be shut down during cleaning.
It is well known that the provision of a strainer in a piping system will cause some pressure drop. When the strainer is relatively clean of debris, the pressure drop is minimal but, when debris builds up and clings to the mesh material forming the strainer, the pressure drop can be considerable, bordering between 1 and 3 PSI. Therefore, in automatic, self-cleaning straining systems, pressure sensitive devices are placed both upstream and downstream of the strainer, and the pressure drop is measured across the strainer. At a preset and predetermined pressure drop across the strainer, a valve is actuated to drain the system and carry away the debris clinging to the strainer material, which is removed therefrom by spraying the strainer and the debris stored in the drainage pipe to which the valve is connected. Typically, this automatic, self-cleaning strainer system is set to be actuated when there is a pressure differential between 1 and 3 PSI, which is approximately equal to that condition where 50% of the strainer open area is clogged by debris. Another means by which automatic self-cleaning may be carried out is to use timed, periodic cleaning, without guaging the pressure drop across the strainer. Of course, the frequency of such self-cleaning may be varied to suit the particular environment in which the strainer is placed. Automatic, self-cleaning strainers are usually and typically used for piping systems carrying water, since it is easier to dispose of the drained water than another liquid not easily disposed of. Automatic self-cleaning also has the advantage of allowing less open area for strainer per given cross-sectional area of piping, since it is cleaned more often and, usually, more thoroughly.
In systems that are carrying medium that contain a large degree of sediment, solid particulates, rust, and the like, it is common to provide a pair of similar straining devices in parallel, which is generally termed a "duplex formation." This duplex formation allows the use of one strainer at a time, with the other shut off so that it may be cleaned. Appropriate manifolds connect the two parallel and similar straining devices, and valves control the flow of the flowing medium in the piping system through one or the other straining device. This duplex arrangement of straining devices is especially useful in cases where strainers become clogged quite often, requiring frequent cleaning.
The present invention is directed to a straining device mounted in-line with the system. That is, the straining device is directed to that class of strainers mounted parallel to the flow of the flowing medium in the piping system, so that the flowing medium passes from one portion of the piping system to the next directly through the strainer, rather than traveling from the portion of the piping system to the strainer in a curved or zigzag path. The advantage of an in-line straining device is that the pressure drop across the strainer is considerably reduced, since therre are no zigzag or curved paths by which the flowing medium must first pass to flow to the straining device and, thereafter, to flow from it back into the main piping system. Another advantage of such an in-line straining device is that it is generally simpler and less expensive to produce and install.
One of the disadvantages that have hitherto prevailed in such in-line straining devices is that cleaning of the straining material has proven difficult and of times impossible, thereby necessitating complete replacement of the straining device. Furthermore, even if replacement and/or repair of the strainer were possible in an in-line straining device, access to the plate mounting the strainer mesh in the main body casing of the device is extremely difficult, time consuming and entirely manual. The prior-art technique of cleaning the strainer requires a spray nozzle above the wire mesh forming the strainer, with the attendant shut down of the system, to allow for such cleaning, flushing and drainage of the sprayed water and released debris. While it is possible to provide automatic self-cleaning in an in-line straining device, without having to shut off the flow of the flowing medium of the piping system, the prior-art structure and technique have proven that it is costly and cumbersome to do so, requiring a re-routing or curved path for the flowing medium which, to some extent, defeats the purpose of using an in-line strainer in the first place: To wit, creation of a smaller pressure drop across the strainer body. Furthermore, in systems that require frequent cleaning of the straining device, the automatic, self-cleaning devices of the in-line type have proven expensive and less than satisfactory.